Hurricane Dean

[Mark Farnik]

At this point it looks almost dead certain that Dean is going to devastate Jamaica on Sunday night. This storm has got its act together much more quickly than everyone anticipated and by the time it reaches Jamaica, if it continues on this rapid intensification trend, it could easily be a Cat 5 by tomorrow morning.
The best case scenario would be Dean landfalling on Jamaica during an ERC, a la Katrina. While Dean would probably only weaken to a low end Cat 4, 140 mph winds are a lesser evil than 160 mph winds. But if Dean hits Jamaica right after it completes an ERC or in between ERC's, extreme 160+ mph sustained winds with gusts over 180 mph are well within the realm of possibility. Also, Dean's windfield has increased dramatically in the last 12 hours, with hurricane force winds now extending over 85 miles from the center and tropical storm force winds over 220 miles out from the center, and it continues to expand with little signs of slowing any time soon, so it will siginificantly impact a much larger area wherever it makes landfall.

Looking ahead, call it a gut feeling, I suspect Dean's encounter with Jamaica is going to nudge his path more to the north than the NHC and the models anticipate and Dean is going to take a slightly sharper right turn than forecast, which would cause the storm to scrape by or just miss the Yucatan, hopefully sparing Cozumel and Cancun, which are still recovering from the desctruction wrought by Wilma two years ago. But while possibly sparing the Yucatan from absolute devastation, this deviation would shift the landfall about 100 miles to the north, which would shift the bullseye from Brownsville/Matamoros to Corpus Christi. Also, if Dean's eye spends less than 6 hours over the Yucatan, the disruption to the storm would be minimal and he would be back to his full fledged vicious self in no time. But if Dean somehow manages to thread the needle through the Yucatan Channel, God help the Gulf Coast.

The bottom line attm is this: with nothing but practially non-existent shear, limited land interactions and simmering SST's ahead of him, Dean is likely going to become one of the most intense Atlantic hurricanes on record. Once he recovers from his encounter with Jamaica and moves over the torrid waters of the western Caribbean, Dean may very well challenge Wilma's status as most intense Atlantic hurricane on record in the Monday/Tuesday timeframe. And realizing that this is only the 'D' storm and it's only mid August, one has to wonder just how bad it's going to get once we hit mid to late September...

 

[MClarkson]

Think of it this way. Dean has a few days to play with these warm waters, and there is nothing to prevent it from becoming a 5 at some point. Dean will likely cycle eyewalls for the next few days, varying between a upper 3 and a 5.

The current satellite image is the last for a few hours due to the nightly eclipse. Looks decent. Cloud tops have warmed slightly and the CDO pattern is a little less symetrical, but the eye is nearly perfect, a good indicator of an epic storm. It looks like outflow to the southwest might be impeded slightly, but is still excellent everywhere else. After this pass the plane is coming home I think, so Dean will be on its own for a few hours(although you might be able to get a low angle shot from goes-west) Then we get the satellite back around 07z and another plane should be there around 12z.


passing through the northeast eyewall the plane has just found 154 knot flight level winds, which would reduce to a standard surface estimate of 138 knots, borderline cat 4/5. SFMR was not working well during that pass.

050330 1506N 06627W 6944 02705 9478 +103 +103 096136 148 999 999 05
050400 1507N 06627W 6971 02758 9990 +082 +999 089150 154 121 034 05
050430 1508N 06627W 6991 02795 9990 +075 +999 086143 146 112 040 01

 

[Brandon Clement]

At this point it looks almost dead certain that Dean is going to devastate Jamaica on Sunday night. This storm has got its act together much more quickly than everyone anticipated and by the time it reaches Jamaica, if it continues on this rapid intensification trend, it could easily be a Cat 5 by tomorrow morning.
The best case scenario would be Dean landfalling on Jamaica during an ERC, a la Katrina. While Dean would probably only weaken to a low end Cat 4, 140 mph winds are a lesser evil than 160 mph winds. But if Dean hits Jamaica right after it completes an ERC or in between ERC's, extreme 160+ mph sustained winds with gusts over 180 mph are well within the realm of possibility. Also, Dean's windfield has increased dramatically in the last 12 hours, with hurricane force winds now extending over 85 miles from the center and tropical storm force winds over 220 miles out from the center, and it continues to expand with little signs of slowing any time soon, so it will siginificantly impact a much larger area wherever it makes landfall.

Looking ahead, call it a gut feeling, I suspect Dean's encounter with Jamaica is going to nudge his path more to the north than the NHC and the models anticipate and Dean is going to take a slightly sharper right turn than forecast, which would cause the storm to scrape by or just miss the Yucatan, hopefully sparing Cozumel and Cancun, which are still recovering from the desctruction wrought by Wilma two years ago. But while possibly sparing the Yucatan from absolute devastation, this deviation would shift the landfall about 100 miles to the north, which would shift the bullseye from Brownsville/Matamoros to Corpus Christi. Also, if Dean's eye spends less than 6 hours over the Yucatan, the disruption to the storm would be minimal and he would be back to his full fledged vicious self in no time. But if Dean somehow manages to thread the needle through the Yucatan Channel, God help the Gulf Coast.

The bottom line attm is this: with nothing but practially non-existent shear, limited land interactions and simmering SST's ahead of him, Dean is likely going to become one of the most intense Atlantic hurricanes on record. Once he recovers from his encounter with Jamaica and moves over the torrid waters of the western Caribbean, Dean may very well challenge Wilma's status as most intense Atlantic hurricane on record in the Monday/Tuesday timeframe. And realizing that this is only the 'D' storm and it's only mid August, one has to wonder just how bad it's going to get once we hit mid to late September...

Andrew, Camille and Katrina were all August Hurricanes so it is not that uncommon to get strong hurricanes this time of the year. The F storm is next in line but everything before it was junk with the exception of Dean.

Jamaica didn't make Gilbert make any sort of turn north and Dean's track, projected track and intensity are nearly identical to Gilbert.

I'm not saying it wont happen just that it is pretty unlikely.

On September 3rd, a westward moving tropical wave showing no signs of organization emerged
off the northwest African coast into the North Atlantic. Over the next several days, a broad area
of low pressure formed whose circulation extended nearly to the equator. An organized center
was not evident until it approached the Windward Islands on the 8th. By the 9th, it had developed
into the 12th tropical depression of the season 400 miles east of Barbados.

The depression moved west-northwest at 17 mph, reaching tropical storm strength over the
Lesser Antilles on the afternoon of the 9th. Rapid strengthening ensued on the 10th, bringing
Gilbert to hurricane-force that evening. The system continued its trek west-northwest, passing
over Jamaica as a major hurricane on the 12th. After it emerged into the northwest Caribbean
Sea, Gilbert rapidly intensified into a category 5 hurricane, with recon reports ranging between
882-885 hPa for the hurricane's surface pressure on the afternoon of the 13th. It moved into the
Yucatan peninsula, becoming the first category 5 hurricane to make landfall in the Atlantic Basin
since Camille in 1969.

Gilbert tracked west-northwest through the Gulf of Mexico as a category 3 hurricane, making its
final landfall in northeast Mexico just north of La Pesca on the afternoon of the 16th. As the
weakening system moved across Texas and Oklahoma, heavy rains fell along its path, as it
accelerated northeast thru the Mid-Mississippi Valley into the Great Lakes late on the 19th/
early on the 20th. Below is the track of this cyclone, provided by the National Hurricane
Center.

http://www.hpc.ncep.noaa.gov/tropical/rain/gilbert1988.html


I found this model of Gilbert. Pretty similar circumstances too. You have the big Bermuda high, Low pressure over the Gulf out in front. Not exactly the same but pretty darn close.

More models, Satellite shots and plenty of words Large file warning (PDF). The screen shot above is on page 54.
http://www.aoml.noaa.gov/general/lib/lib1/nhclib/nwstechmemos/techmemo45.pdf

 

[Blake Michaleski]

As mentioned in the latest discussion, Bouy 42059 should see some extreme winds here shortly.

Winds are already gusting to over 48 kts.

http://ndbc.noaa.gov/station_page.php?station=42059

 

[MClarkson]

good point, this bouy could take a direct hit in 2 hours or so. Think it survives? Waves are allready 27 feet.


00z hurricane runs are in. Not much change for either of them. The HWRF seems to have a better handle on the intensity in the near term. Both take the storm just north of jamaica, then GFDL goes well north and the HWRF goes for cancun, in much better agreement with the global models.

Edit: GOES-east is out of eclipse and the CDO pattern is more symetrical, the eye still nearly perfect.

 

[John Peters]

CDO looks a bit disrupted in recently VIS images. Perhaps the storm ingested some dryer air? Otherwise it's possible that we are seeing the beginning of an eyewall replacement cycle - there are signs of concentric eyewalls on the IR images.

800 AM NHC Advisory keeps the storm at 150 mph sustained/930 mb CP

 

[Marko Korosec]

What impresses me the most is the pressure drop in the last 24h... 46hPa from 09z yesterday! That was some rapid intensification, from 976hPa to 930hPa at 09z this morning.

According to latest dropsonde data from 1212z SP is at 926hPa with 145kt FL winds. Looks like its going through eyewall replacement cycle, indeed.

 

[John Peters]

What impresses me the most is the pressure drop in the last 24h... 46hPa from 09z yesterday! That was some rapid intensification, from 976hPa to 930hPa at 09z this morning.

According to latest dropsonde data from 1212z SP is at 926hPa with 145kt FL winds. Looks like its going through eyewall replacement cycle, indeed.

actually based on the most recent satellite images, the storm probably ingested some dryer air - it appears that CDO is becoming more organized again, and the onset of eyewall replacement cycles are usually associated with a rise in pressure (initially).

 

[Gene Moore]

RE: SA, most of the tornadoes were brief, dropping from low clouds moving very fast and impossible to chase or detect (e.g., wall clouds, etc.), at least in the metro area. It might be easier now with onboard radar. It has been my experience that tornadoes near the main circulation core (once inland) are rather difficult to chase and see. Jim? I don't recall any "wedge" reports, but that might have occurred in isolated cells away from the core or in the bands.

FYI: I did an extensive ground survery in 2000 of the area between Corpus-Brownsville and Corpus-Houston. Between Corpus and Brownsville, Highway 77 could be a serious problem if you were trapped on that lonely highway with a Cat-4+. I don't recall many places worth shooting in that area and there was little infrastructure, at least in 2000. In addition, ALL gas stations along the highway in towns like Armstrong were closed. The area between Corpus and Houston is also a challenge. Locals may know more and please post and correct me if you know of any new survivable vantage points in that area.Warren

As for your comments on highway 77, totally true and a bad road to be on during a big event. This road will flood, there is no help anywhere close if a chaser gets trapped by high water and as Warren mentions there is no place to hide. Tim Marshall got pinned down on that road during a night hurricane, probably the one your were discussing. That said, if the eyewall is just north of Brownsville chasers will go for that road. I'll also include that south TX has been very aggressive about closing roads in the last 5 years.

Off topic: On your SA comments.... I wasn't sure where you were in the storm when the tornadoes were reported. I'll agree the ones near the center are almost impossible to catch unless the camera is running when one screams by. As for the wedge report, it was real and I saw the video and read documentation. And true, it was from a spiral band supercell away from the main circulation.

Gene Moore

 

[Marko Korosec]

actually based on the most recent satellite images, the storm probably ingested some dryer air - it appears that CDO is becoming more organized again, and the onset of eyewall replacement cycles are usually associated with a rise in pressure (initially).

According to the latest dropsonde data at 1340z it appears that pressure slightly rised to 929hPa, not sure if that came from ERC or from some dry air intrusion before.

I am thinking where it will go over Jamaica...or it will pass it just along the south/north coast...hope people are prepared there...it doesn' look good.

 

[John Peters]

According to the latest dropsonde data at 1340z it appears that pressure slightly rised to 929hPa, not sure if that came from ERC or from some dry air intrusion before.

I am thinking where it will go over Jamaica...or it will pass it just along the south/north coast...hope people are prepared there...it doesn' look good.

yeah, hard to tell based on the satellite images whether the CDO/eyewall symmetry was disrupted by an eyewall replacement cycle or dry air intrusion... looks like it is possible that the storm is developing concentric eyewalls.

Look at this image of floyd on the morning of sept 13, 1999. The storm displays a similar erosion of CDO on its western side; however, floyd regained symmetry later in the day and intensified.
http://www.atmos.umd.edu/~stevenb/hurr/99/floyd/floyd124.n15.sep13_1305.gif

 

[beaudodson]

Just posted 15 new (large) Gempak Images for those interested

http://www.beaudodson.com/blog/blog3.htm

 

[Brian Stertz]

Looks like another hit on the Cancun-Cozumel Mexico area again. This time it could be even worse unfortunately. Hurricane Wilma was real bad to Cozumel according to my friends pictures and this time....Dean looks like it will pass overhead...or possibly just north based on the NHC forecast track. At any rate, Cozumel should get hammered again....and Dean looks to be a more progressive forward system than Wilma.

 

[beaudodson]

Live info from Jamaica (if anyone knows of any ham nets online can you post the links)

http://stormcarib.com/reports/current/jamaica.shtml

 

[rdale]

Any thoughts to breaking this up into FCST / NOW / REPORT / DISC threads from here on out now that we have chasers en route?